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authorAdrian Kummerlaender2018-05-20 23:57:39 +0200
committerAdrian Kummerlaender2018-05-20 23:57:39 +0200
commit3bc6622f4f339a9ab3c808d02c48c1c144bc4e10 (patch)
treedc0b1bb1270b4eba4faa10f9f15e57b0ac99f5d5 /src
parent85e988e16feddd67be6466fe02dbbaaa2ef61545 (diff)
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Render particles to texture
Preparation for drawing particle trails using multiple transparent textures.
Diffstat (limited to 'src')
-rw-r--r--src/main.cc102
1 files changed, 100 insertions, 2 deletions
diff --git a/src/main.cc b/src/main.cc
index d381f01..8a1d6de 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -69,10 +69,38 @@ GLint setupComputeShader() {
return shader;
}
+GLint setupTextureShader() {
+ GLint shader = glCreateProgram();
+ glAttachShader(shader, compileShader(R"(
+ #version 330 core
+ layout (location = 0) in vec2 screen_vertex;
+ layout (location = 1) in vec2 texture_vertex;
+ out vec2 TexCoords;
+
+ void main() {
+ gl_Position = vec4(screen_vertex, 0.0, 1.0);
+ TexCoords = texture_vertex;
+ }
+ )", GL_VERTEX_SHADER));
+ glAttachShader(shader, compileShader(R"(
+ #version 330 core
+ out vec4 FragColor;
+ in vec2 TexCoords;
+ uniform sampler2D screen_texture;
+
+ void main() {
+ FragColor = texture(screen_texture, TexCoords);
+ }
+ )", GL_FRAGMENT_SHADER));
+ glLinkProgram(shader);
+ return shader;
+}
+
int window_width = 800;
int window_height = 600;
float world_width, world_height;
glm::mat4 MVP;
+GLuint FramebufferID;
void updateMVP() {
world_width = 20.f;
@@ -94,7 +122,12 @@ void updateMVP() {
void window_size_callback(GLFWwindow*, int width, int height) {
window_width = width;
window_height = height;
+
+ glBindFramebuffer(GL_FRAMEBUFFER, FramebufferID);
+
glViewport(0, 0, width, height);
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, window_width, window_height, 0, GL_RGB, GL_UNSIGNED_BYTE, (void*)0);
+
updateMVP();
}
@@ -145,6 +178,22 @@ int main() {
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
+ glGenFramebuffers(1, &FramebufferID);
+ glBindFramebuffer(GL_FRAMEBUFFER, FramebufferID);
+
+ GLuint TextureID;
+ glGenTextures(1, &TextureID);
+ glBindTexture(GL_TEXTURE_2D, TextureID);
+ glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, window_width, window_height, 0, GL_RGB, GL_UNSIGNED_BYTE, (void*)0);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+ glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+ glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, TextureID, 0);
+
+ if ( glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE ) {
+ std::cerr << "Texture framebuffer error" << std::endl;
+ return -1;
+ }
+
glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
updateMVP();
@@ -173,9 +222,43 @@ int main() {
GL_STATIC_DRAW
);
+ glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
+ GLuint QuadVertexArrayID;
+ glGenVertexArrays(1, &QuadVertexArrayID);
+ glBindVertexArray(QuadVertexArrayID);
+ GLuint QuadVertexBufferID;
+ glGenBuffers(1, &QuadVertexBufferID);
+ glBindBuffer(GL_ARRAY_BUFFER, QuadVertexBufferID);
+ std::vector<GLfloat> quad_buffer_data{
+ -1.f, 1.f, 0.f, 1.f,
+ -1.f, -1.f, 0.f, 0.f,
+ 1.f, -1.f, 1.f, 0.f,
+
+ -1.f, 1.f, 0.f, 1.f,
+ 1.f, -1.f, 1.f, 0.f,
+ 1.f, 1.f, 1.f, 1.f
+ };
+ glBufferData(
+ GL_ARRAY_BUFFER,
+ quad_buffer_data.size() * sizeof(GLfloat),
+ quad_buffer_data.data(),
+ GL_STATIC_DRAW
+ );
+ glEnableVertexAttribArray(0);
+ glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4*sizeof(GLfloat), (void*)0);
+ glEnableVertexAttribArray(1);
+ glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4*sizeof(GLfloat), (void*)(2*sizeof(GLfloat)));
+
+ GLuint TextureShaderID = setupTextureShader();
+ GLuint ScreenTextureID = glGetUniformLocation(TextureShaderID, "screen_texture");
+ glUniform1i(ScreenTextureID, 0);
+
auto lastFrame = std::chrono::high_resolution_clock::now();
do {
+ glBindFramebuffer(GL_FRAMEBUFFER, FramebufferID);
+
// update particles at most 50 times per second
if ( std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - lastFrame).count() >= 20 ) {
glUseProgram(ComputeShaderID);
@@ -188,10 +271,10 @@ int main() {
lastFrame = std::chrono::high_resolution_clock::now();
}
- glClear(GL_COLOR_BUFFER_BIT);
-
glUseProgram(ShaderID);
+ glClear(GL_COLOR_BUFFER_BIT);
+
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glBindBuffer(GL_ARRAY_BUFFER, VertexBufferID);
@@ -200,6 +283,20 @@ int main() {
glUseProgram(0);
+ glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
+ glUseProgram(TextureShaderID);
+
+ glBindTexture(GL_TEXTURE_2D, TextureID);
+ glBindBuffer(GL_ARRAY_BUFFER, QuadVertexBufferID);
+ glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4*sizeof(GLfloat), (void*)0);
+ glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4*sizeof(GLfloat), (void*)(2*sizeof(GLfloat)));
+
+ glClear(GL_COLOR_BUFFER_BIT);
+ glDrawArrays(GL_TRIANGLES, 0, 6);
+
+ glUseProgram(0);
+
glfwSwapBuffers(window);
glfwPollEvents();
}
@@ -211,6 +308,7 @@ int main() {
glDeleteVertexArrays(1, &VertexArrayID);
glDeleteProgram(ShaderID);
glDeleteProgram(ComputeShaderID);
+ glDeleteFramebuffers(1, &FramebufferID);
glfwTerminate();